How do I draw a circle in a location in my video
In blender's VSE we don't have exact control of timing, we can only align to a frame. To get a timing of half a second you will want to use an even number of frames, at 24 fps 12 frames will be 500ms.

To get the dot in place you want an image of the dot, save it as a png so you have the alpha channel to easily clear out everything but the dot. In the VSE add the image, ensure it is above your video, then in the strip properties N set the blend type to Alpha Over and set the frame length what you want.



To position the spot, under strip input, enable Image Offset and change the X and Y values until it is in place. You could also create an image the same resolution as your video and place the dot where you want it.



Then smile as you see the dot on your video.